The present invention relates to a signal transmission system for transmitting signals from a driving circuit to a receiving circuit through a transmission line.
As long-distance data transmissions between information processing units or the like become faster in recent years, a waveform distortion caused by the attenuation of a transmitted signal through a transmission line such as a cable or a printed wiring board becomes one of the problems to be addressed. Several attempts have been made to reduce a waveform distortion caused by the attenuation. Such attempts include: the shortening of a distance required for data transmission; the improvement in a transmission line; the improvement in the performance of circuit such as the addition of an equalizer or the addition of an emphasizer; or the development of a high-accuracy receiver circuit. However, these attempts take much time and costs to provide additional components and develop individual circuits and transmission lines.
In the conventional signal transmission system described above, therefore, there are several problems that need to be addressed. For example, much time and costs are required to improve a transmission line to make an addition of specific circuit or the like for reducing the waveform distortion caused by attenuation of transmitted signal through the transmission line.
An object of the present invention is to provide a signal transmission system which reduces a waveform distortion caused by the attenuation of a transmitted signal through a transmission line without having to use additional specific circuit or the like and also without having any improvement of its transmission line.
According to one aspect of the present invention, a signal transmission system is provided which includes: a driving circuit with a characteristic impedance of Zs; a receiving circuit for receiving the signal from the driving circuit; and a transmission line for transmitting a signal from the driving circuit to the receiving circuit, wherein the transmission line includes a first transmission line with a characteristic impedance of ZsO connected to the driving circuit and a second transmission line with a characteristic impedance of ZO connected to the receiving circuit, wherein the relationship between the characteristic impedance ZsO and the characteristic impedance ZO is adjusted to satisfy a mathematical relation of: Zs less than ZsO less than ZO, and wherein a time obtained by doubling a transmission time of the first transmission line is shorter than a rise time and a fall time of the signal at an output end of the second transmission line.
According to one aspect of the present invention, a signal transmission system is provided which includes: a driving circuit with a characteristic impedance of Zs; a receiving circuit for receiving the signal from the driving circuit; and a transmission line for transmitting a signal from the driving circuit to the receiving circuit, wherein the transmission line includes a first transmission line with a characteristic impedance of ZsO connected to the driving circuit and a second transmission line with a characteristic impedance of ZO connected to the receiving circuit, wherein the characteristic impedance Zs, the characteristic impedance ZsO and the characteristic impedance ZO is defined to make the signal input to the receiving circuit overshoot, and wherein a time obtained by doubling a transmission time of the first transmission line is shorter than a rise time and a fall time of the signal at an output end of the second transmission line.